عنوان مقاله [English]
connective [statement] is among the foundations of Sinean logic. In the Logic of Shifa, it has been divided into evident and non-evident necessary as well as into various kinds of necessary in terms of necessity and necessary in terms of facts. Without knowing and understanding various kinds of necessary, the nature of necessary connective, its rules, its relation to various kinds of entailment in the modern logic, and the structure of necessary connective cannot be understood and known. Thus, in the present article, after providing Ibn Sina's definition for evident and non-evident necessary connective and analyzing and criticizing some views posed in this concern, I analyze views introduced by Ibn Sina and some later logicians about necessary connective in terms of necessity and in terms of facts (or, as put by Khwajah, verbal and true necessary). Then, I examine and criticize some views posed in this regard which, I think, have gone in wrong direction and got far from Ibn Sina while speaking of Ibn Sina.
According to the results of the present study, firstly, division of necessary into evident and non-evident in Ibn Sina's Shifa has nothing to do with division of conditional into necessary and accidental. Secondly, in dividing necessary into evident and non-evident, Ibn Sina has relied upon the factual world and the necessary relations existing in it. Thus, it should not be thought that such a division is merely based upon logical and merely formal relations. Thirdly, according to Ibn Sina, the necessary connective statement "if five is even, then it is a number" is true in terms of necessity and false in terms of facts. Thus, the reason provided by him for falsity of this connective statement concerns facts and should not be confused with the station of necessity. Fourthly, Ibn Sina's argument for falsity of the above connective statement in terms of facts is a continuous and integrated one consisting of various steps none of which should be regarded as an independent argument. Furthermore, this argument has been stated in the language of predicative logic (and not in the language of propositional logic) and has nothing to do with the fallacy of hiding in the relevance logic.
Thus, the idea that division of necessary connective into evident and non-evident corresponds to division of connective into accidental and necessary is not consistent with the contents of Shifa and the present author's interpretation of it. Nor is the idea that Ibn Sina has regarded a necessary with impossible precedent as a necessary connective in terms of necessity and thought that it is false in factual world consistent with his distinction between two stations of necessity and facts.